Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	$ 275,834		$ 275,834			$ 276,288
Less: accumulated depreciation and amortization	(190,624)		(190,624)			(186,799)
Total property, plant, and equipment, net	85,210		85,210		$ 81,421	89,489
Depreciation expense	7,700	$ 7,500	15,100	$ 14,800
Land
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	634		634			644
Buildings
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	3,986		3,986			24,558
Furniture and fixtures
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	13,561		13,561			13,121
Machinery and equipment
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	27,089		27,089			27,452
Equipment leased to third parties under operating leases
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	29,633		29,633			30,093
Leasehold improvements
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	127,368		127,368			111,247
Computers and software
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	$ 73,563		$ 73,563			$ 69,173